Many kinds of stents are quite frequently used in cardio-vascular surgery for the purpose of providing a supporting structure for anatomical vessels. More specifically, stents are often placed at the site of a stenosis in a vessel to establish and maintain the patency of the vessel. This, of course, may be necessary in order to allow for the continued flow of blood through the vessel. Not surprisingly, the deployment and accurate placement of a stent in the vessel of a patient requires a great deal of skill.
As difficult as it may be to deploy and emplace a stent, the effort required to retrieve a misplaced stent can be equally as difficult, if not more so. To appreciate this, first consider how a stent is placed in a vessel such as an artery. Typically, the stent is deployed into the vessel of a patient with the stent mounted over the balloon of a balloon catheter. As so mounted, the stent is passed through a previously positioned guiding catheter and to the desired location in the vessel. Actual placement of the stent in the vessel is then accomplished by extending the stent and balloon catheter beyond the distal end of the guiding catheter where the balloon can then be inflated at the target site. This balloon inflation extends the stent and then separates the stent from the balloon upon balloon deflation. At this point, if, as sometimes can happen, trouble is encountered in delivering the stent to the target site prior to deployment, the stent should be retrieved. The retrieval of a stent from a body vessel necessarily requires the engagement of a retrieval instrument with the stent. Ideally, because the placement catheter is already in place, the stent can be withdrawn into the placement catheter and then removed from the vessel without stent dislodgement. Engagement of the placement catheter with the stent, however, can be troublesome. Specifically, during withdrawal of the stent into the placement catheter, it can happen that the stent snags on the catheter. Most often, this snagging occurs at or near the distal end of the placement catheter. Further, the problem can be aggravated by the presence of a relatively soft distal tip which is typically attached to the distal end of the catheter to reduce trauma to the patient.
Should the stent become snagged or the distal end of the catheter, the balloon, which has only the ability to expand the stent, will be of little value in retrieving the stent. On the other hand, the present invention recognizes that the placement catheter may, itself, be helpful in accomplishing the task of retrieving the stent.
In light of the above, it is an object of the present invention to provide a device for retrieving a stent from the vessel of a patient which can grip onto and hold the stent during its removal from the vessel. Yet another object of the present invention is to provide a device for retrieving a stent from the vessel of a patient which is simple to use, relatively easy to manufacture and comparatively cost effective.